WASHINGTON — Donald John Trump will be inaugurated as the 45th president of the United States on Friday, ushering in a new and more unpredictable era in which he has vowed to shatter the established order and restore American greatness.
From the West Front of the Capitol, overlooking what may be hundreds of thousands of admirers and onlookers on a day when rain threatens, Mr. Trump plans to use his Inaugural Address to promise that he will use the next four years to rebuild the nation’s economy, reassert control over its borders and regain respect for the United States around the world.
Mr. Trump, wearing a dark suit with red tie and accompanied by Melania Trump in a powder-blue suit, intends to waste little time after taking the 35-word oath that will be administered by Chief Justice John G. Roberts Jr. to start unraveling the policies of his departing predecessor, President Obama. Within hours of taking office, the new president could begin signing executive orders freezing regulations put in place in the last weeks of Mr. Obama’s tenure and reversing policies on health care, immigration and other areas.
“It all begins today!” Mr. Trump wrote in a Twitter post. “I’ll see you at 11:00 A.M. for the swearing-in. THE MOVEMENT CONTINUES — THE WORK BEGINS.”
While Mr. Trump showcased his pugilistic style during the transition, aides said he would use the ceremony Friday to call for national unity. “In the Inaugural Address, you will hear an uplifting, aspirational, visionary Donald Trump calling for us to take bold action fairly quickly,” Kellyanne Conway, his incoming White House counselor, told CBS News. “That’s what businessmen do.”
Through a long day of pomp and pageantry that will end with three inaugural balls, Mr. Trump will have the opportunity to revel in his moment of triumph. Surrounded by relatives, lawmakers, former presidents and other dignitaries, including Mr. Obama, and the Democrat he beat last November, Hillary Clinton, Mr. Trump will take command of a country unsettled after one of the most polarizing periods in modern times.
His critics have made clear they will not defer even for a day to a new leader they accuse of playing to racism and hatred. Demonstrators gathered early Friday morning to protest the new president. Liberal groups have organized a march that they expect to draw as many as 200,000 to downtown Washington on Saturday.
For Mr. Trump, the ceremonies will cap a remarkable rise to power that defied all expectations, and his ascension amounts to a hostile takeover of a capital facing its most significant disruption in generations. While officially a Republican, Mr. Trump has at times assailed leaders of both parties and positioned himself as the ultimate outsider, making clear that he will follow his own instincts in determining the nation’s course.
America has never seen a president quite like Mr. Trump, the son and grandson of immigrants who grew up to become a real estate magnate, casino owner, beauty pageant operator and reality television star whose tumultuous love life played out on tabloid front pages.
Never before has the presidential oath been administered to someone who had never served either in public office or as a general in the military. At age 70, Mr. Trump will become the oldest president ever sworn in for the first time and the first born in New York since Franklin D. Roosevelt.
He will also be one of the wealthiest presidents ever to enter the White House, with far-reaching business ties that have already raised questions about where his interests end and the country’s begin. He arrives in the Oval Office dogged by reports about Russian interference in the election on his behalf and, in the hours before his inauguration, fresh word of a federal investigation into the Russian ties of some of his advisers.
But Mr. Trump overcame the skeptics who did not take him seriously when he embarked on what seemed like a quixotic bid for the presidency. An Ivy League-educated mogul who lives in a tower with an 80-foot-long living room in the heart of the nation’s largest city, he turned himself into the unlikely leader of a populist movement rooted away from the country’s urban and suburban coasts.
His bracing candor, disregard for convention and willingness to offend whole sections of the population to make a point came across as refreshing truth telling to many Americans disenchanted with politically correct Washington elites in both parties. But his constant quarrels and impulsive Twitter storms have alienated many others, leaving him with the lowest support in polls of any president entering office in modern times.
He takes over on Friday without much of a team in place. Although he has named nominees for every cabinet post, the Senate confirmation process has slowed and few sub-cabinet officials have been announced. Mr. Trump has asked more than 50 officials from Mr. Obama’s administration, particularly in security agencies, to stay temporarily to ensure the continuity of government.
For the nation’s 58th inauguration, Mr. Trump opted largely to follow tradition. He and Mrs. Trump, a former supermodel from Slovenia, started the day at a service at St. John’s Episcopal Church across Lafayette Square from the White House, then made the short trip to the executive mansion for coffee with Mr. Obama and his wife, Michelle. From there, the two presidents will share a limousine for the short motorcade to the Capitol.
In addition to Mr. Obama, former Presidents Jimmy Carter, Bill Clinton and George W. Bush are attending the ceremony, though all four opposed Mr. Trump’s election. The elder President George Bush remained hospitalized in Houston, where he was recovering from pneumonia. More than four dozen House Democrats announced they would boycott the event in protest.
Three religious leaders representing different faiths were to offer invocations. Cardinal Timothy M. Dolan, the Roman Catholic archbishop of New York, who once accused Mr. Trump of “nativism,” will lead off, followed by the Rev. Dr. Samuel Rodriguez of the National Hispanic Christian Leadership Conference and Pastor Paula White, a prominent televangelist from Florida.
Michael Richard Pence will be sworn in first as vice president by Justice Clarence Thomas. Mr. Pence, 57, a former governor and congressman from Indiana, plans to place his hand on Ronald Reagan’s Bible as his wife, Karen, and three adult children, Michael, Charlotte and Audrey, look on.
For his own oath, Mr. Trump will place his hand on two Bibles, one given him by his mother in 1955 just before his ninth birthday and the other used by Abraham Lincoln when he was inaugurated in 1861 and again by Mr. Obama in 2009 and 2013.
Standing nearby will be Mrs. Trump and the new president’s grown children from two previous marriages, Donald Jr., Eric, Ivanka and Tiffany. Also on hand will be Ivanka’s husband, Jared Kushner, who will serve as an unpaid senior adviser in his father-in-law’s White House. Mr. Trump’s son, Barron, 10, did not attend the morning events but was expected to attend the swearing-in; he will remain in New York with Mrs. Trump until the end of the school year.
With the completion of the oath, the Marine Band is scheduled to play “Ruffles and Flourishes” four times and then “Hail to the Chief,” followed by a 21-gun salute.
After Mr. Trump’s Inaugural Address there will be benedictions from Rabbi Marvin Hier, founder of the Simon Wiesenthal Center; the Rev. Franklin Graham, reprising a role his father, the Rev. Billy Graham, often played; and Bishop Wayne T. Jackson, who runs Great Faith Ministries International and Impact Network, which calls itself the only Christian television network founded and operated by African-Americans.
Jackie Evancho, a 16-year-old who earned fame as the runner-up on the television show “America’s Got Talent” in 2010, is scheduled to sing the national anthem.
Other artists declined to participate, including Jennifer Holliday, who canceled her appearance just days before the event after a backlash from gay and lesbian fans. The Mormon Tabernacle Choir will perform, despite an online petition signed by 36,000 people and the resignation of one of its members. So will the choir from the Washington National Cathedral, over the objections of the cathedral’s most recent dean.
As other presidents have before him, Mr. Trump was to share a lunch of lobster, beef and chocolate soufflé with lawmakers in the Statuary Hall of the Capitol before traveling back down Pennsylvania Avenue to the White House, where he will watch the inaugural parade from the temporary bandstands erected for the occasion.
In a city where Mr. Trump won just 4 percent of the vote, many residents fled town for a long weekend, leaving many downtown streets empty even outside of the security zone guarded by an extensive phalanx of thousands of police officers and military personnel.
After eight years in power, Mr. Obama will make his exit, heading after the ceremony by helicopter from the Capitol to Joint Base Andrews in suburban Maryland, where he plans to address a crowd of former aides and allies.
He and Mrs. Obama will then board the presidential jet, no longer designated as Air Force One, for a flight to Palm Springs, Calif., for a vacation before returning to Washington.
The Obamas have rented a house not far from the White House to allow their youngest daughter, Sasha, to finish high school, making Mr. Obama the first president to stay in Washington after leaving office since Woodrow Wilson.
Just hours before his departure, Mr. Obama took to Twitter, expressing his gratitude to his 13.6 million followers and hinting that he did not intend to fade quietly away. He asked for their thoughts and vowed to continue to be politically active.
“I won’t stop; I’ll be right there with you as a citizen, inspired by your voices of truth and justice, good humor, and love,” Mr. Obama said, directing people to a video message on a new website for his foundation, Obama.org. In the video, Mr. Obama, joined by Mrs. Obama, pledged to make the foundation a “living, working center for citizenship” around the world.
For their part, Vice President Joseph R. Biden Jr. and his wife, Jill Biden, intend to head by train to Delaware, which he represented in the Senate for 36 years. But they too plan to return part-time to Washington, where Mrs. Biden teaches community college in the Virginia suburbs.